Use the Workbook Open event to display a message for a specific excel
workbook;
Set the security level to low/medium in (Tools|Macro|Security). From
workbook press Alt+F11 to launch VBE (Visual Basic Editor). From the left
treeview search for the workbook name and click on + to expand it. Within
that you should see the following
VBAProject(Your_Filename)
Microsoft Excel Objects
Sheet1(Sheet1)
Sheet2(Sheet2)
Sheet3(Sheet3)
This Workbook
Double click 'This WorkBook' and paste the below code to the right code pane.
Private Sub Workbook_Open()
MsgBox "Message to be displayed"
End Sub